sql get row count

I. Introduction of row migration and row link in actual work we often encounter some problems with low Oracle database performance. Of course, there are many reasons that cause low Oracle database performance, we can use some correct design and

SQL tuning is primarily about reducing the number of consistent gets and physical reads. COUNT (1) is compared with COUNT (*): If your datasheet does not have a primary key, then count (1) is faster than COUNT (*)If you have a primary key, the

　　First look at a commonly used table structure design method:Then you may encounter a typical query method, the Master Table Association, query the child table of some (or all) key points corresponding to the value, landscape display (that is, the

For more information about bugs fixed in SQL Server 2000 Service Pack 4, click the following article number to view the article in the Microsoft Knowledge Base:314128 FIX: When an RPC call is performed, Access with conflicting values includes an

Row chain: When a row is too large to fit into any block, row chaining occurs. in this case, the Oracle devide the row into smaller chunks. each Chunk is stored in a block along with the necessary poiters to retrive and assemble the entire row.

--trunc (Date,[fmt])/trunc (Number[,decimals])SELECT sysdate from dual;SELECT TRUNC (sysdate) from dualSELECT TRUNC (12.34524,2) from dual; --12.34SELECT TRUNC ( -12.34724,2) from dual; --12.34SELECT TRUNC (12.34524,-1) from dual; --10--Returns the

Summary of row-to-column issues1, Row to column---1, the simplest row to column/*Question: Suppose there is a student score table (TB) as follows:Name Course ScoreZhang San language 74Zhang San Mathematics 83Zhang San Physics 93John Doe Language

MS SQL Server Query optimization methodThere are many reasons for the slow speed of queries, which are common1, no indexes, or no indexes (this is the most common problem with query slowness, is the flaw in programming)2, I/o throughput is small,

Because of the row link can only increase db_block_size to clear, and db_block_size after the creation of the database can not be changed, so there is no more than the purge of the row link, mainly for the row migration to talk about in the actual

The Count (*) or COUNT (1) or count ([column]) in the database is probably the most commonly used aggregate function. A lot of people actually have a clear distinction between the three. This article will describe the roles, relationships, and